Lines on the map, cables across oceans

The shape of the telegraph network was informed by existing historical trade routes and determined by where ships could easily go. S. Prashant Kumar, a historian of science and empire, offers more information:

"Telegraph networks were overlaid on trade networks. The movement of ships and people and goods and commodities, is what these physical, electrical networks that form the telegraph were overlaid on top of. And there's obviously the economic reason that what's moving across these telegraph wires is information about prices, information about which ships are going to end up where. So if you were in a port in Hong Kong, you could go to your Telegraph office and find out about the price of opium in Bihar, or you could figure out which ships were docking at Singapore in two weeks, and so it is integrated with this physical network. But it is also that the laying of these cables proceeds along shipping routes for technological reasons. You can't lay cables for most of the 19th century in these deep ditches, which is also where currents and storms are worse, so ships tend to stay away from that deep open water until [there were] steamships. What that means is that people are laying telegraph cables along shipping routes – so these maps are integrated." - S. Prashant Kumar